1. Technical Field
Example embodiments of the present invention relate in general to a radio communication system and more specifically to a method of allocating radio resources and an apparatus for performing the same, which can enhance resource-use efficiency.
2. Related Art
The Long Term Evolution (LTE) system and/or the LTE-advanced system of the 3rd Generation Partnership Project (3GPP) support(s) a plurality of radio bearers to one mobile terminal, for providing services having various characteristics to mobile terminals. That is, mobile terminals receive a service through radio bearers having different qualities of service (QoSs) depending on a desired QoS.
In the LTE or LTE-advanced system, when a mobile terminal performs initial access, a base station sets one default radio bearer. Here, a service is provided through the default radio bearer depending on a current radio resource state, with no consideration of QoS.
Subsequently, when provision of a QoS-requiring service to a mobile terminal is started, the base station allocates a dedicated radio bearer to the mobile terminal, allocates resources on the basis of provided QoS information (for example, traffic transmission priority, transmission rate, delay time, etc.), and transmits traffic to the mobile terminal using the allocated resources. At this point, when there are simultaneously traffic to be transmitted through the default radio bearer and traffic to be transmitted through the dedicated radio bearer, the base station may allocate more resources to the dedicated radio bearer than the default radio bearer on the basis of the provided QoS information and thus transmit more traffic through the dedicated radio bearer, or allocate all available resources to the dedicated radio bearer without allocating any resources to the default radio bearer and thus transmit all traffic through the dedicated radio bearer whose QoS is assured.
That is, the base station performs multiplexing for all radio bearers which are set between the base station and the mobile terminal, for transmitting traffic to the mobile terminal, and distributes resources (which are used to transmit the traffic) to a plurality of radio bearers in consideration of priority and a transmission rate depending on the QoS characteristics of the radio bearers.
Moreover, the base station adjusts the amount of data transmitted to the mobile terminal depending on a channel state. That is, when the channel state is poor because the mobile terminal is located far away from the base station, the base station selects a low modulation scheme to transmit a small amount of data, and when the channel state is good because the mobile terminal is located near the base station, the base station selects a high modulation scheme to increase a data transmission rate.
The base station selects a modulation scheme on the basis of channel quality indicator (CQI) information reported from the mobile terminal. For example, the base station decides a modulation and coding scheme (MCS) such that a block error rate (BLER) of a physical layer becomes 0.1% or less, depending on a CQI value reported from the mobile terminal.
That is, the base station first decides a traffic transmission amount to be transmitted to the mobile terminal on the basis of a CQI transmitted from the mobile terminal, allocates resources within a range of the traffic transmission amount which has been decided depending on the QoS characteristic of the radio bearer allocated to the mobile terminal, and transmits traffic.
According to the above-described conventional resource allocation method, an MCS is first selected on the basis of a CQI value reported from a mobile terminal such that the BLER of the physical layer becomes 0.1% or less, a data transmission rate is decided, and resources are allocated within a range of the decided data transmission rate. For this reason, the conventional resource allocation method is not suitable for a specific service sensitive to delay.
For example, since a real-time service such as a video service is sensitive to delay, by fundamentally applying a forward error correction (FEC) scheme (for example, error resilient video coding, forward erasure recovery, scalable video coding, etc.) for preventing delay caused by retransmission due to a packet error, the real-time service can be recovered even when loss occurs within a certain range (for example, 5% or less).
Therefore, when data is transmitted by applying a BLER of 0.1% or less to all traffic for minimizing packet loss in a radio channel, a serious error can be caused. For example, when resources are allocated to a dedicated radio bearer (which is used to transmit video traffic in which a desired data transmission rate is 10 Mbps and a loss rate of 5% is allowable) so as to provide a data transmission of 9.5 Mbps to a mobile terminal for adjusting a BLER to 0.1% in the physical layer, the mobile terminal cannot use a corresponding service.